<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script type="text/javascript">
    var sours = prompt("请输入成绩", "100")
    switch (true) {
        case 90 <= sours && sours < 100:
            console.log("优秀");
            break;
        case 80 <= sours && sours < 90:
            console.log("良好");
            break;
        case 60 <= sours && sours < 80:
            console.log("及格");
            break;
        default:
            console.log("废材");
            break;
    }
</script>
</body>
</html>